[Continuing the series on the structure of academic conversation which began here.] 

In the previous post on this topic I mentioned the negative features of disagreement, namely, that they distract attention and energy that could be used more productive. I left open the question of scenarios in which disagreement serves a creative purpose, but thankfully Bryan Caplan addresses one important aspect of this:

Mill states it well: "He who knows only his own side of the case knows little of that."  If someone can correctly explain a position but continue to disagree with it, that position is less likely to be correct.  And if ability to correctly explain a position leads almost automatically to agreement with it, that position is more likely to be correct.  (See free trade).  It's not a perfect criterion, of course, especially for highly idiosyncratic views.  But the ability to pass ideological Turing tests - to state opposing views as clearly and persuasively as their proponents - is a genuine symptom of objectivity and wisdom.

This seems like a straightforward proposition: being engaged enough in a disagreement that you can adequately and accurately restate your opponents position means that you have given a significant amount of thought to their position and yet have chosen to retain your own. This implies at least some degree of self-examination, and thus a sort of "inoculation" against at least some set of counterarguments.

Notice that I began with engagement. Disagreements are productive when both parties agree that having the debate is worthwhile. This is, I think, what separates many debates in the more esoteric areas of science--social, natural, whatever--from policy debates. People can generally see the significance of determining whether or not to keep bombing Libya, even if it is not a particularly salient issue to them personally (i.e., from the perspective of an average American rather than an average Libyan). On the other hand a more technical point about, say, what level of statistical accuracy is appropriate for a normative argument, can easily seem inane to an observer who is not engaged in the conversation.

I've been thinking of a number of examples to demonstrate this, ranging from the American West to religion, but I hate to reason by analogy and at least one person has already proposed a Christian-Atheist Turing test. That should be interesting, and if both sides actually try to follow the protocol of the Turing test it will be both surprising and refreshing. It also raises the question of whether there are some issues for which one opposing view just can't encompass the other. I believe that there are. The next post on this will be ever-so-slightly more practical less abstract.